Quiet check valve for pulsating flow

ABSTRACT

A check valve (4) with spherical, spring-loaded valve head (25) is used for pulsating flows, especially in a fuel injection system for Otto engines. As a result of low flow resistance, such check valves have had a tendency to cause noise when the valve head (25) strikes down against the valve seat (11) during pulsating of the flow caused by selective opening of the fuel injection nozzles. The valve head (25) is designed with a flange (7) downstream of the valve seat (11), and this flange (7) interacts with a narrow boring (13) during the first part of the opening stroke. Consequently, a secondary throttling (12) is formed, in addition to the primary throttling between the valve head (25) and the valve seat (11), which contributes to the valve head being forced away at a distance from the valve seat. During the movement of the valve head towards the seat, the flange first comes down into the boring (13), as a result of which the continued movement of the valve head towards the seat is damped by the volume of fluid which lies between flange (7) and seat (11), as a result of which noise is prevented from occurring.

The invention relates to a check valve with means that quiet noise thatmight be generated by a pulsating flow past the valve.

State of the Art

A check valve has a valve head which is urged against a valve seat by aspring. The known valve head is spherical. A flange across the path offlow is formed downstream of the valve head. There are a large number ofsolutions for preventing noise when valve heads in check valves orcock-operated valves close against a valve seat.

In Swedish patent SE,C, 139 389, a solution is disclosed for preventingthe thin film of liquid, which passes between the valve head and theseat in an almost closed position, from causing a whistling noise. Byvirtue of the fact that the throughflow channel, upstream of the valveseat, is designed with axially running grooves in the channel wall,disintegration of the film of liquid is brought about before it passesthe valve head. Consequently, the valve head can be kept in a minimalopening position without a passing film of liquid causing a whistlingnoise.

In American patent U.S. Pat. No. 3,735,777, progressive throttling ofthe flow in a check valve is brought about when the flow exceeds a givenvalue. Downstream of the ordinary check valve seat, there is in thiscase a second valve seat, against which the valve head closes, counterto the action of a check valve spring, when the flow becomes too great.By virtue of the fact that the channel walls taper towards this secondseat and are formed with grooves running in the direction of flow withdecreasing flow cross-section, progressive throttling is brought about.This damps the speed of the valve head towards the closing position sothat a fully developed flow is not closed off abruptly.

A solution for preventing clattering check valves is shown in Americanpatent U.S. Pat. No. 3,782,412. In this case, a cylindrical valve headruns in a narrow circular throughflow channel so that only a narrow gapis formed between the valve head and the channel. By virtue of the factthat the cylindrical valve head is plane-machined on its outer surfacein only three places of four generatrices distributed evenly over thecircumference, a lateral force is brought about on the valve headtowards the channel wall in the event of developed flow. Consequently,the valve head adheres against the wall so that small flow fluctuationsdo not cause the valve head to strike down against the valve seat.

A check valve which to a certain extent reduces the noise which isbrought about when the check valve strikes against the seat is shown inAmerican patent U.S. Pat. No. 3,532,115. In this case, the valve headhas a first sealing body in the form of a rounded elastic valve headwhich allows deformation of the valve head until a more rigid collardownstream on the valve head comes into contact around the valve seat.

Another check valve, which in the first instance is intended forintermittent flow with short opening times of high frequency, is shownin German Patent Application DE,A,36 12 393. In order to give the valvehead improved control in the throughflow channel so that the valve headis centred against the seat in the sealing position, the valve head isin this case designed with recesses, evenly distributed around thecircumference, upstream of the parts on the valve head which come intocontact against the seat.

The previously known check valves do not, however, have any constructivemeasures for damping the movement of the valve head down towards theseat apart from the damping which is afforded by the throttling betweenthe valve head and the seat. As the valve head of a check valve isconventionally designed as a sphere or hemisphere in order to reduce theflow resistance over the check valve, this means that a small flowfluctuation can cause a rapid movement of the valve head towards theseat. The valve head can to a certain extent be made elastic andshock-absorbing, but such a design does not reduce the speed of thevalve head upon movement towards the seat, as a result of which noisecan still arise. For example, in check valves in injection systems forpetrol engines, the valve head must be resistant to petrol, which meansthat relatively rigid rubber material must be used in the firstinstance. This rigid rubber material affords good sealing but, as far asnoise generation is concerned in the event of striking against the valveseat, the noise reduction is small.

OBJECT OF THE INVENTION

The object of the present invention is to provide an improved quietcheck valve with low pressure drop, which is suitable for pulsatingflow, especially as a check valve in an injection system for fuel forOtto engines. These injection systems often include a check valve whichis to ensure that the fuel is retained in the pipes and is not drainedback to the fuel tank when the engine is switched off. If in thisconnection the check valve has a ball-shaped or spherical valve headwhich affords low pressure drop and has a characteristic which affordsrapid response to the flow and its fluctuations, the valve head of thecheck valve comes to strike back against the valve seat at high speedand cause the valve head to end up in a state of self-oscillation. Thisself-oscillation is evident in the idle speed of the combustion engine,and lies around 1000 Hertz depending on the spring characteristic of thecheck valve.

For the purpose of solving these problems, the check valve according tothe invention has a valve body with a channel in it which is defined bya wall around the flange that is downstream of the valve head, and thewall is shaped and sized to form a throttling gap between the outer edgeof the flange and the channel wall. The channel wall is shaped aroundthe flange over the path of the valve head so that the gap has a firstflow area during one part of the opening stroke of the valve head and anincreasing flow area during a later part of the opening stroke.

The invention results in the valve head being forced, with developedflow, to take up a position at a distance from the valve seat and, withdeveloped flow, a volume of fluid between the flange and the valve seatbeing used as damping fluid for the movement of the valve head towardsthe valve seat. Consequently, the spherical valve head can lie andself-oscillate on a distance from the valve seat without causing noise.

Embodiments of the invention are indicated, which have proved to beparticularly advantageous. These include the throttling gap beingsymmetric around the flange and the valve head and include particulardimensions and flow characteristics of the throttling gap. Otherfeatures and advantages of the invention emerge from the attacheddescription of an exemplary embodiment. The description is made withreference to the attached drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a complete check valve in partial cross-section,

FIG. 2 shows the lower part of the check valve in cross-section with analternative check valve seat,

FIG. 3 shows a check valve structure, which forms part of the checkvalve, in partial cross-section,

FIG. 4 shows the check valve structure in FIG. 3 seen in the viewIV--IV,

FIG. 5 shows the valve seat structure in FIG. 2 seen from above,

FIG. 6 shows the valve seat structure in FIG. 5 in the cross-sectionVI--VI, and

FIG. 7 shows the valve head.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

FIG. 1 shows a complete check valve arranged in a coupling nipple 1which is intended to be coupled to a fuel pump (not shown) by means ofthe coupling part 3. Also connected to the nipple 1, by means ofthreading onto the coupling part 2, is a fuel pipe (not shown) for acombustion engine. The pump is to suck fuel from a fuel tank andpressurise the pipes of the fuel system with the fuel. In order that thefuel will not drain back to the fuel tank after the pump has beenswitched off, the coupling nipple includes an integrated check valve 4.This has the purpose of retaining the fuel in the fuel pipes so that theengine can be restarted immediately after the engine/pump has beenswitched off and that the formation of air bubbles in the pipes of thefuel system is prevented.

Injection systems for Otto engines are preferably adapted for injectionoverpressure of 2.5-3.0 bar, and, if a check valve with low pressuredrop is used, a weaker and cheaper pump can be used. If spherical orball-shaped valve heads are used in the check valve, a check valve withlow pressure drop is obtained, but which instead in these circumstancesdisplays great instability in the developed flow. As, moreover, the flowis subjected to fluctuations on the one hand from the pump element ofthe fuel pump and on the other hand from sequential opening of theinjection nozzles, the instability of the valve head is furtherinfluenced. The fuel pump can be a gear pump which is driven by anelectric motor. With an operating speed of the pump of around 6000 rpmduring idle running of the combustion engine and with 11 pump elementsin the pump, the flow is thus imparted a pulsation of fully 1000 Hertz.Moreover, the superimposed pulsation from the sequential opening of thefuel injection nozzles is received.

The housing 16 of the coupling nipple, and thus of the check valve, ispreferably manufactured in one single piece, for fuel systemsexpediently of POM (polyoximethylen) plastic. By virtue of the fact thatthe nipple is angled, a spring-loaded 6 check valve 4 can simply bemounted through the inlet before an insert 8, which forms the valve seattowards the inlet, is fastened. The valve seat structure 8 canpreferably also be manufactured from POM plastic. The valve head 25itself consists of a rubber valve head 25 which, via a distance element5, is acted upon by a coil spring 6 towards a valve seat 11 formed onthe valve seat structure 8 and counter to the direction of flow F.Consequently, the fuel can be pumped into the inlet 9 and, counter tothe action of the check valve 4, reach the outlet 10 and, in the eventof reversed flow, block the check valve 4 against the valve seat 11.

The distance element 5, which is shown in FIGS. 3 and 4, is designed inits lower part with a mounting recess 23 adapted to the valve head 25.The valve head 25 (FIG. 7), which is manufactured from a fuel-resistantrubber material, is formed with a coupling part 27 which, by means of apress fit, is pushed firmly into the mounting recess 23. For improvedretention of the coupling part 27 of the valve head in the mountingrecess 23, the recess 23 can be designed with gripping flanges 24 whichproject radially into the recess and grip into the coupling part 27 ofthe rubber valve head. For interaction with the check valve spring 6,the upper part of the distance element 5 is designed, on itscross-shaped structure, with a shoulder 21 for centring and control ofthe coil spring 6. In order to prevent bottoming of the spring in theevent of compression, the upper part of the distance element is extendedso that a stop shoulder 22 is formed.

According to the present invention, the check valve 4 is designed with awasher or radially projecting flange 7 between the valve head 25 itselfand the distance element 5. A part of the flange 7, projecting radiallyin relation to the valve head, contributes then with an increase in thearea facing the flow of over 100 percent. By virtue of the fact that thethroughflow channel is formed with a first boring 13, situateddownstream of the valve seat, at the height of the flange 7 in a closedposition, which is adapted in such a manner that its diameter exceedsthe flange diameter by a few percent, a second throttling 12 is formedin addition to the throttling between the valve head 25 itself and thevalve seat 11. This throttling 12 has a constant throughflow area in afirst part of the opening stroke of the check valve 4, followed by agradually increasing throughflow zone 14 during a second part of thestroke. The gradually increasing throughflow zone 14 increases thethroughflow area so that, in a third and final part of the stroke, athroughflow area corresponding to or exceeding the inlet area of theinlet 9 of the check valve 4 is obtained. The gradually increasingthroughflow zone 14 can either be terminated at opposite ends if thezone in a rear edge, in the direction of flow, on the valve seatstructure 8, shown in FIG. 1, or merge into a constant throughflow zone15 in the valve seat structure 8, shown in FIG. 2.

In a preferred exemplary embodiment with a nominal developed flow ofbetween 120 and 150 liters per hour, the components which are criticalfor the invention have the following dimensions:

valve head diameter: 5 millimeters

flange diameter: 7.2 millimeters

inlet diameter: 4 millimeters

first boring diameter: 7.4 millimeters

gradual increase to diameter: 8.8 millimeters.

These values mean that the second throttling between the flange 7 andthe first boring 13 amounts to 17 percent of the inlet diameter and thatthe gap in the throttling is 0.1 millimeters wide during the first partof the stroke of the check valve. A part of the way into the second partof the stroke, the same throughflow area is obtained as at the inlet,after which during the third part of the stroke to the end an increaseof 60 percent is achieved in the throughflow area. In an operating casefor a fuel injection system, in which the flow amounts to 130liters/hour and in which the pressure drop over a fully opened checkvalve amounts to 0.2 bar, a check valve with a flange diameter of only7.0 millimeters and other dimensions as above immediately makes thestriking noises typical for check valves when the valve head bouncesagainst the seat. An increase of the flange diameter to 7.1 millimetersmeans that the noise begins to decrease while a flange diameter of thepreferred 7.2 millimeters means that the check valve becomes quietwithout the valve head bouncing against the seat. This shows that theconstant throttling formed between the flange and the first boringduring the first part of the stroke is of great importance for obtaininga quiet check valve for pulsating flow.

The area reduction in the throttling 12 relative to the inlet shouldpreferably fall below 25 percent and/or the gap width should be lessthan 0.15 millimeters. The area increase as a result of the flange 7should at the same time itself be of significant dimension, that is tosay of the order of magnitude of 100 percent and expediently within therange 70-150 percent. In order that the valve head in the preferredembodiment be forced away from the seat at a safe distance, the firstboring 13 interacts with the flange 7 for 20 percent of the strokelength or effective working stroke of the check valve. Depending uponthe dimensions of the check valve, this interaction will take place overa part of the stroke length which is inversely proportional to thenominal developed flow through the check valve and proportional to thewidth of the gap. However, this interaction should take place over atleast 10 percent of the working stroke of the valve head.

This interacting design of valve head, flange and valve seat means that,when the flow starts to be developed, the valve head 25 is forced tolift from the valve seat 11 to a position in which the flange lieswithin the gradually increasing throughflow zone 14. In the event offully developed flow, the flange of the valve head comes to find aposition of equilibrium, in which the resulting force from the pressuredrop over the check valve 4 corresponds to the force from the spring 6.This position of equilibrium can arise within the gradually increasingthroughflow area 14 or during the last part of the stroke in the boring15. The spring will of course be adapted for the pressure drop which isobtained with the intended flow developed for this so that the desiredposition of equilibrium is obtained.

A contributory factor for the unstable check valve with spherical valvehead not giving rise to noise during developed flow, when the valve head25 and flange of the check valve are imparted a movement towards thevalve seat, is that the flange then goes down into the first boring 13and that the volume of liquid situated between the flange 7 and thevalve seat 11 then functions as damping fluid. This volume of liquidthen forms a damping cushion which cushions the movement of the valvehead 25 towards the seat 11 while the remaining flow which passes thethrottling channel 12 is sufficient to hold the valve head 25 from theseat 11.

By means of the preferred embodiment, a spherical valve head, whichseals against a cone-shaped seat, is made use of with the advantageswhich these valves have with regard to pressure drop, response andsealing capability. By means of the check valve according to theinvention, effective damping is obtained of the movement of the valvehead against the valve seat and, during developed pulsating flow, thevalve head lies at an adequate distance from the valve seat, so that anoscillation of the valve head caused by the flow pulsation does not leadto noise.

Merely a spherical valve head interacting with the channel walls doesnot afford an equally great safety margin against the occurrence ofnoise as the valve head 25 and flange 7 which form the subject of theinvention. This is because merely a sphere has such low flow resistancethat a small negative flow fluctuation immediately imparts to thespring-loaded valve head 25 a movement towards the seat which leads tostriking through against the seat. In the deliberate design of the valvehead 25 and the flange 7, a valve head is obtained which, in interactionwith the first boring 13 of the channel wall, forms a throttling channel12 which effectively prevents strikethrough.

In an alternative embodiment (not shown), the gradual throughflow zone14 can, instead of a linearly increasing diameter of the channel wall,consist of recesses, running in the direction of flow and of a sizewhich increases in the direction of flow, in a channel wall whichotherwise has the same diameter as the first boring 13. These recessesare then expediently distributed symmetrically in the direction of thecircumference over the channel wall so that the valve head does not comeinto unbalance in the transverse direction. The recesses are, however,not to begin until after the first part of the check valve stroke.

In terms of manufacturing, the check valve itself can also be givenanother composition than the embodiment demonstrated according to thesubject of the invention. The projection forming the flange 7 on thedistance element 5 can of course consist of a loose washer which duringassembly is clamped firmly between distance element and valve head. Thecoil spring 6 acting on the check valve can also be placed alternativelybetween a non-movable distance element 5 which bears permanently againstthe inner wall of the coupling nipple and an axially movable compositevalve head and washer.

The complete check valve, apart from spring 6 and valve head 25, ispreferably manufactured from POM plastic. The distance element is thenpremounted expediently with valve head and spring, after which this canbe inserted as a unit into the inlet 9. Mounting is concluded by thevalve seat structure 8 being threaded into the inlet and preferablywelded together with the valve housing 16 by means of ultrasonicwelding. For this welding, the valve structure 8 is designed with aridge 17 which is formed in the contact surface and is plasticallydeformed against the corresponding contact surface of the valve housingduring welding.

We claim:
 1. A check valve comprising:a valve body having an internalwall shaped to define a flow channel through the valve body, the flowchannel having a flow inlet and a flow outlet spaced away from theinlet; a valve seat in the channel at the wall, the seat having anopening through it for passage of liquid past the seat; a valve headdisposed in the channel, the valve head having a seating part of a sizeand shape to engage and cooperate with the valve seat for blockingreturn flow through the channel past the valve seat and toward theinlet, said valve head seating part being at least partly sphericalwhere it contacts the valve seat, said valve head having an openingstroke length in the channel; a flange on the valve head locateddownstream in the channel from the seating part, the flange having anouter peripheral edge toward the channel wall and the flange having across section in the channel out to the peripheral edge of the flangewhich exceeds the cross section in the channel of the seating part ofthe valve head; the channel wall having a first part which is shaped todefine a relatively narrower opening valve seat for contacting theseating part of the valve head; the wall having a second part thatdefines a first throttling gap between the flange outer edge and thechannel wall, the first throttling gap being downstream of the valveseat, the wall second part being so placed and of such a length as toextend around the valve head and around the flange as the valve headseating part shifts downstream off the valve seat or shifts upstream inthe direction toward the valve seat; the second part of the channel wallbeing shaped and of such length that the first throttling gap has afirst flow cross sectional area during a first part of the openingstroke of the valve head seating part off the valve seat and for a firstdistance of movement of the valve head toward the channel outlet, thefirst throttling gap extending along the channel over at least 10% ofthe opening stroke length of the valve head, the flange cooperating withthe first throttling gap to prevent substantial flow when the flange isadjacent the second wall part and forcing the valve head to a safedistance from the valve seat during developed flow thereby preventingvalve noise during pulsating flow; the wall having a third partdownstream in the flow direction from the second part and placed toextend around the outer edge of the flange over a second part of theopening stroke of the flange and the valve head toward the outlet, thethird part of the wall defining a second throttling gap between theperipheral edge of the flange and the wall, the second throttling gaphaving a gradually increasing cross section of flow area in the secondpart of the opening stroke of the valve head and the flange away fromthe valve seat toward the channel outlet.
 2. The check valve of claim 1,wherein the wall defines a circular cross section channel; the at leastpartly spherical part of the valve head has a respective first diameter,the flange is annular with a circular periphery, the flange having agreater diameter than the first diameter of the at least partlyspherical part of the valve head.
 3. The check valve of claim 1, whereinthe valve head seating part is at least partly curved where it contactsthe valve seat.
 4. The check valve of claim 3, wherein the valve seat isdefined in the valve body generally at the inlet to the channel.
 5. Thecheck valve of claim 3, further comprising a spring normally urging thevalve head toward engagement with the valve seat.
 6. The check valve ofclaim 3, wherein the valve seat has a gradually widening incline awayfrom the channel inlet and toward the channel outlet, and the seatingpart of the valve head engages the inclined portion of the valve seat.7. The check valve of claim 6, wherein the wall defining the channel iscircular, the valve seat is uniformly shaped and annular, the valve headis so shaped and positioned and the flange is so shaped and positionedthat the first and second throttling gaps are symmetrical around theflange and the valve head.
 8. The check valve of claim 3, wherein thefirst and second throttling gaps extend along the channel over at least10% of the stroke length of the valve head.
 9. The check valve of claim3, wherein the first and second throttling gaps extend along the channelover approximately 20% of the stroke length of the valve head.
 10. Thecheck valve of claim 3, further comprising a stop in the valve body forstopping movement of the valve head away from the valve seat, fordefining the stroke length of the valve head from the valve seat,through the first and second parts of the opening stroke of the valvehead, and to the stop.
 11. The check valve of claim 10, wherein thefirst and second throttling gaps extend along the channel over at least10% of the stroke length of the valve head.
 12. The check valve of claim11, wherein the second part of the channel wall is of constantcross-section so that the first part of the throttling gap is of aconstant cross-section to provide a flow restriction past the flangesuch that the flow area through the first part of the throttling gappast the peripheral edge of the flange is less than 25% of the flow areathrough the inlet of the check valve.
 13. The check valve of claim 3,wherein the second part of the channel wall is of constant cross-sectionso that the first part of the throttling gap is of a constantcross-section to provide a flow restriction past the flange such thatthe flow area through the first part of the throttling gap past theperipheral edge of the flange is less than 25% of the flow area throughthe inlet of the check valve.
 14. The check valve of claim 3, whereinthe second part of the channel wall is shaped to provide a constant flowarea through the first part of the throttling gap and past theperipheral edge of the flange during the first part of the openingstroke of the valve head; andthe third part of the channel wall isshaped to define a gradual increase in the flow area through the secondpart of the throttling gap past the flange during the second part of theopening stroke of the valve head.
 15. The check valve of claim 14,wherein the third part of the channel wall is so shaped that during thesecond part of the opening stroke of the valve head, the second part ofthe throttling gap past the flange enlarges to at least 100% of the flowarea of the channel inlet with the valve head off the valve seat. 16.The check valve of claim 2, wherein the flange on the valve head has adiameter which exceeds the diameter of the spherical part of the valvehead by at least 30%.
 17. The check valve of claim 16, wherein theflange and the wall of the channel are respectively so shaped that thefirst part of the throttling gap provides a flow area of less than 3square mm for passing a nominal flow of between 100 and 150 liters perhour.
 18. The check valve of claim 17, wherein the flange and the wallof the channel are respectively so shaped that in the second part of thechannel, the flow area of the first part of the throttling gap isapproximately 25% of the flow area of the inlet to the channel.